OBJECTIVES: a. The profile of a specific cell surface glycolipid and glycoprotein structure has been systematically investigated by combination of cell surface labeling and application of a new endo-Beta-galactosidase of Escherichia freundii. Through this study we have found a common structural unit consists of repeating N-acetyllactosamine in complex glycosphingo-lipid and in Band 3 glycoprotein. These are the carriers for i- and I-antigen. The same technique has been applied to compare the developmental change of fetal to adult erythrocytes and a progressive branching during maturation of erythrocytes has been confirmed. b. On the other hand, modified ganglioside having N-trifluoroacetylneuraminic acid was synthesized which was found to be a potent ganglioside:sialidase inhibitor. c. Eight new gangliosides have been isolated and characterized from human erythrocyte membranes. Some of them have sialosy 12 yields 6 galactose linkage and sialosy 12 yields 3-N-acetyl-galactosamine linkage. Some of them have new core structures. d. Further immunological studies have been carried out that asialo GM2 (ganglio-N-triosylceramide) is a tumor-associated antigen of mice KiMSV tumor.